Ziplock is a brand name for plastic storage bags and many other products made by SC Johnson. The term “Ziploc bag” has become a generic way of referring to any self-sealing bag that is used to store food or other items. Other common names for this product include sandwich bags, snack bags, resealable plastic bags and food storage bags.

Ziploc bags have several different kinds of closures. There is the classic “zip” version, where you press together two interlocking pieces of plastic. Newer bags may have a small tab that runs across the top of the bag to seal it closed. Those who freeze meat, fish or produce may opt for vacuum-sealed bags, which create an airtight seal and keep food extra fresh during its long, cold storage period.

Ziploc bags (and other sandwich bags) are made with a product known as “film” in the recycling industry. Film is clear, thin plastic made of either low-density polyethylene (or LDPE, which corresponds to the recycling #4) or high-density polyethylene (or HDPE, which corresponds to the recycling #2). Most film is recycled into composite lumber, a highly durable building material that is used for decks, benches and playground equipment.

The hardest thing about recycling film is keeping it in your recycling bin. Since the plastic is so lightweight it becomes airborne easily. When it flies out of trashcans and recycling bins it creates litter in neighborhoods and transfer stations — and usually ends up in the nearest dumpster.

Loose Ziploc bags and other types of film plastic often get caught in recycling machinery, damaging equipment and causing downtime at recycling centers. That is why it is very important to carefully follow your community’s guidelines for recycling film.